For many years, efforts have been made by many companies in the plastics industry to develop plastic products (especially floor or chair mats) that possess easy, durable and repeatable folding characteristics and that can be made by simple and economical processes. Prior efforts to achieve solutions to the problem of providing such product and processes, however, have failed to achieve this goal so that there remains a long-felt need in the market for such a product.
Examples of these failed prior "solutions" include U.S. Pat. Nos. 4,448,625 and 4,476,174. These patents disclose a laminated plastic chair mat wherein the mat is made of (1) a semi-rigid plastic portion and (2) has a separate plastic strip laminated therein on the underside of the mat which, when in use, is in contact with the floor surface. After forming, the laminated mat is slit by a knife edge tool which makes a straight cut into the top surface of the mat. Because of this straight cut, an immense amount of stress is created when folding resulting in rapid failure due to cracking or breaking. Thus, the top side of the mat has an uneven surface that is created by the slit. Furthermore, the slit itself is immediately visible to the user.
There are many problems that arise from the use of this solution. For example, the laminate material often is unable to withstand repeated folding operations. Moreover, it is believed that the public would not want to purchase a chair mat that has a slit on the surface that engages the rollers of chairs and the like. In this regard, such a slit would not only be irritating to the user but may even pose a potential safety hazard as well depending upon the width of the slit.
Alternatively, other persons in the industry have attempted to solve this problem by making chair mats having a middle section that is either made of a thinner material or made of a different and more flexible material than the remaining portions of the mat. However, the problem with this so-called solution is that these chair mats do not exhibit a uniformly hard surface in terms of, for example, a chair rolling across them.
In a somewhat related area, folded (as opposed to foldable) plastic products have been formed by cutting plastic sheet material. For example, U.S. Pat. No. 3,292,513 discloses both a method and apparatus for scoring plastic sheet materials so that the material then can be folded and, thereby, formed into containers and other fixed shapes. Thus, it shows a method of scoring that is accomplished by interposing the plastic material between a straight scoring blade means and a platen assembly (see, e.g., FIG. 9 and col. 6, line 62 to col. 7, line 5).
Similarly, U.S. Pat. No. 3,330,001 teaches various methods for making plastic corner pads whereby coils 50 and 52 are used to remove portions of plastic and to, thereby, make U-shaped grooves in the plastic. Thereafter, the corner pads are formed by folding portions of the plastic along the grooves. Significantly, these grooves are not used to make a product that is foldable only in special circumstances such as shipping, handling or storage.
Finally, various types of retractable knife and/or other cutting apparatus are well-known in this field. See, for example, U.S. Pat. No. 4,457,199 which teaches a method of cutting slits into plastic by controlling the blades so that they cut to a depth less than the thickness of the plastic material. Furthermore, U.S. Pat. No. 4,094,217 is directed to a particular cutting apparatus whereby a single sheet may be slit or cut into a plurality of sheets.